The isolated procoagulant protein moieties of thromboplastin (tissue factor) and platelet factor 3 lipoproteins from bovine brain and platelets will be characterized. Their composition and properties are to be defined. Their biological (procoagulant, enzymatic) activities alone and in combination with natural and synthetic phospholipids will be determined. A single step procedure for the purification of the human platelet antiheparin (platelet factor 4) from lysed platelets has been developed. The primary structure of the isolate has been defined. The intact and chemically modified product is being used as a ligand in affinity chromatographic studies on heparin binding to determine which amino acid residues are involved in the expression of antiheparin activity.